MOLLUSCS. 



333 



enouii'h to crush the shell 



a canal, a smooth columella, au J an untootlied outer lij). The most common species is 

 the whelk, li. undatum, common to the northern Atlantic shores of Europe and Amer- 

 ica. It burrows in the sand below low-water mark. Its 

 eggs are laid in hemispherical capsules, yellow in color, i>iled 

 up in a heap, and presenting an ajjpearance well described 

 1 ly tile n:nne ' sea-corn ' applied to them by the New England 

 lisliermen. In England they ai'e called -sea wash-balls' 

 I'rom the fact that they are employed in washing the hands, 

 their parchment-like texture tending to scour away the 

 dirt. Each capsule, when first laid, contains a number of 

 eggs, but of these but few develop, the others being swal- 

 lowed by the young which have got a little start in devel- 

 opment. In this respect, they are like the young sjiiders. 



In America, the whelk is not used as food, but in Eng- 

 land large numbers are brought to the market, the annual 

 catch at Whitstable (a small village at the mouth of the 

 Thames) being worth, in 1866, £12,000. Although the 

 shell of the whelk is stout and strong, it is eaten in great 

 numliers liy the larger bottom-feeding fishes, some of which 

 arc furnished with teeth strong 



like a stone breaker, while others bolt shell and all whole, 

 leaving the gastric juices the labor of dissolving the 

 nutritious portions. 



Besides tlie common Uiicciiiiini ti/idatum, several 

 other species are found in the north Atlantic, north of 

 the New England shores. One of these boreal forms, £. 

 ciliatirm, is figured ; tlie differences between this and the 

 common whelk are evident. Most of the specimens in 

 collections are obtained from the stomachs of fishes caught 

 on the Grand Bank. 



Tiie genus Eburna embraces the ivory shells, so called 

 from the color and texture of some of the forms. In the 

 dozen oriental species comprised in the genus, the shell 

 is thick, deeply umbilicate, the columella and outer lip 

 without folds or teeth, and the suture between the whorls 

 FiG.4i(i.-/" channelled. Tlie surface of the shell is ivory, wliite, 



sjiotted with an orange red. The animals usually move 

 along at a leisurely pace, but when alai-med they are capal:)le of much quicker motions. 

 They frequent muddy bottoms where the water is ten oi- twelve fathoms in de])th, and 

 are caught in considerable numbers in the nets of the Chinese fishermen, who use 

 them as food. 



JSFassa contains a large number of species divided up into the sub-genera, Ilt/anassa, 

 Tritia, etc. The general sh.a]ie and appearance may be seen from our figures, a com- 

 mon character being the tooth or plait at the upper part of the columella, much 

 more marked in some species than in others, and the extensive deposition of enamel 

 on the columellar li|), which not infrequently extends to a considerable distance out- 

 side the aperture. Most of the species are littoral, and at low tide our New Engl.and 

 fiats are covered with mvriads of Nassa trioittata and N'. obsoleta. Farther south a 



